JP2019147140A - Washing method for filter - Google Patents

Abstract

To provide a washing method for a filter that is able to efficiently wash the filter, in drain water treatment equipment to which a filter concentration active sludge method is applied.SOLUTION: A washing method for a filter 6 is used in drain water treatment equipment 1 provided with at least one filter module 7 having a filter 6 with a mesh of 10 μm or larger in a reaction tank 2 storing mixed liquid including drain water and suspended active sludge agitated by aeration. In this washing method, while the filter 6 is soaked in liquid, the filter 6 is washed with ultrasonic sound generated by an ultrasonic sound generator 50 and transmitting in the liquid.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for cleaning a filter that is provided in a reaction tank of a wastewater treatment apparatus and filters a mixed solution.

  Several wastewater treatment technologies for increasing the concentration of MLSS (Mixed Liquor Suspended Solids), which is an indicator of the microbial concentration of a reaction tank, are known. For example, a sponge carrier input activated sludge method, a membrane separation activated sludge method, a dynamic filtration method, a filter concentrated activated sludge method and the like have been developed. Of these, the filter-concentrated activated sludge method cannot obtain as clear treated water as the membrane-separated activated sludge method, but is a treatment method capable of obtaining a level of treated water that can be discharged at low cost and at a low cost. . For example, as described in Patent Document 1, in the filter concentrated activated sludge method, the reaction tank is divided into an upstream section including a raw water inlet and a downstream section including an outlet to a sedimentation section by a partition. . The total amount of the mixed liquid in the upstream compartment passes through the filter attached to the partition (filtered by the filter) and flows out to the downstream compartment. Thereby, high concentration of MLSS in the upstream section of the reaction tank is realized. The filter used in the filter concentrated activated sludge method is, for example, a filter having an opening of about several tens of μm.

JP 2017-189769 A

  The membrane separation activated sludge method is also a technique for filtering the mixed liquid through a membrane to increase the concentration of MLSS, but the opening (pore diameter) of the membrane is smaller than that of the filter used in the filter concentrated activated sludge method. Therefore, the filter used in the membrane separation activated sludge method requires periodic cleaning with a chemical. On the other hand, since the filter used for the filter concentration activated sludge method has a large opening (rough), the filter can be prevented from being clogged for a certain period of time only by cleaning with aerated air necessary for the aerobic treatment. However, when the wastewater treatment apparatus is operated for a long period of time, the sludge that cannot be washed away with aerated air accumulates on the surface of the filter, or a biofilm is formed on the surface of the filter, resulting in a decrease in permeation flux. there is a possibility.

  Then, an object of this invention is to provide the washing | cleaning method of the filter which can wash | clean a filter efficiently in the waste water treatment apparatus to which the filter concentration activated sludge method was applied.

  In one embodiment of the present invention, at least one filter module including a filter having an opening of 10 μm or more is provided in a reaction tank that contains a mixed liquid containing activated sludge in a suspended state and wastewater that is stirred by aeration. In the wastewater treatment apparatus, the filter is cleaned by ultrasonic waves transmitted through the liquid by generating ultrasonic waves with the ultrasonic generator while the filter is immersed in the liquid.

  According to this filter cleaning method, the ultrasonic waves generated by the ultrasonic generator are transmitted through the liquid and transmitted to the filter. The ultrasonic waves act on the filter, and sludge and biofilm attached to the filter are peeled off from the filter. Sludge and biofilm adhered to the inside and back side (filtrate side) of the filter that cannot be washed with aerated air can also be peeled off. Therefore, the filter can be efficiently washed in the wastewater treatment apparatus to which the filter concentrated activated sludge method is applied.

  In some embodiments, the filter module includes a support member that has an opening larger than the opening of the filter and is attached to the filter to support the filter, and is supported by ultrasonic waves that are transmitted through the liquid when the filter is cleaned. The member is vibrated. According to this method, ultrasonic waves are transmitted to the support member, and the support member is vibrated. For example, there is an effect that the support member serves as a vibration medium to vibrate the filter. Therefore, peeling of sludge and biofilm is promoted, and the filter can be washed more efficiently.

  In some embodiments, the filter module includes a frame portion including a side surface to which the filter is attached and an upper surface that is higher than the water surface of the reaction vessel and is open upward. The ultrasonic generator of the ultrasonic generator is positioned in the frame through the opening, and the filter is washed from the back side by the ultrasonic wave transmitted through the liquid mixture as the liquid. According to this method, ultrasonic cleaning can be performed through the open portion on the upper surface of the frame portion. For example, ultrasonic cleaning with the filter module installed is possible. Since it is not necessary to remove the filter module from the waste water treatment apparatus, the filter can be easily and easily washed.

  In some aspects, the at least one filter module has N (N is an integer greater than or equal to 2) filter modules, and M (N is an integer greater than or equal to 1 and less than N) of the N filter modules. While the filtration by the filter modules is stopped, the filters of the M filter modules are washed by ultrasonic waves, and the filtration by (NM) filter modules is performed. According to this method, it is possible to clean the filters of the M filter modules while performing the filtration with the (N−M) filter modules. Therefore, the ultrasonic cleaning of the filter can be performed without stopping the operation of the waste water treatment apparatus.

  According to some aspects of the present invention, a filter can be efficiently washed in a wastewater treatment apparatus to which the filter concentrated activated sludge method is applied.

It is a figure which shows schematic structure of the waste water treatment equipment which concerns on one Embodiment of this invention. It is a top view of the waste water treatment apparatus of FIG. It is a disassembled perspective view of a filter module. FIG. 4A is a diagram illustrating an example of a filter cleaning method, and FIG. 4B is a diagram illustrating a filter that is cleaned using an ultrasonic generator. It is a figure which shows the test result of the washing | cleaning test of the filter in a simulation drainage water flow test.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

  As shown in FIGS. 1 and 2, the waste water treatment apparatus 1 is an apparatus for treating waste water such as sewage. The waste water treatment apparatus 1 decomposes a treatment target (for example, organic matter, nitrogen compound, etc.) contained in the waste water. The waste water treatment apparatus 1 holds activated sludge that is an aggregate of microorganisms in the reaction tank 2. The waste water treatment apparatus 1 causes the mixed liquid 10 formed by mixing activated sludge and waste water to stay in the reaction tank 2 and biologically treats the above-described treatment object. That is, in the waste water treatment apparatus 1, a kind of activated sludge method is used. The object to be treated may be only an organic substance, or may be a nitrogen compound in addition to the organic substance. The waste water treatment apparatus 1 is not limited to sewage, and any waste water can be applied as long as it is organic waste water.

  The waste water treatment apparatus 1 realizes a treatment method (that is, a filter concentrated activated sludge method) that can increase the MLSS concentration, not the so-called standard activated sludge method. The MLSS concentration in the reaction tank in the standard activated sludge method is generally about 2000 to 4000 mg / L. On the other hand, the MLSS concentration in the reaction tank 2 in the wastewater treatment apparatus 1 is a level equal to, for example, the MLSS concentration in the membrane separation activated sludge method, and is, for example, 6000 mg / L or more. The MLSS concentration in the wastewater treatment apparatus 1 can be set to, for example, 10,000 mg / L or more.

  The waste water treatment apparatus 1 contains a reaction tank 2 that contains the mixed liquid and treats the waste water with activated sludge, and a post-treatment tank 15 that contains the treatment liquid (filtrate) treated in the reaction tank 2 and further treats it. Prepare. The reaction tank 2 is, for example, a rectangular water tank whose upper surface is open, and activated sludge that is an aggregate of microorganisms is introduced into or grown in the reaction tank 2.

  The reaction tank 2 has an inlet 3 for introducing waste water to be treated. The inflow port 3 is provided on one side of the reaction tank 2, and the post-treatment tank 15 is provided so as to be adjacent to the other side of the reaction tank 2. A plurality of diffuser tubes 4 are arranged at the bottom of the reaction tank 2. Air is sent to these diffuser tubes 4 from an air supply means such as a blower outside the reaction tank via an air supply pipe 14, and the liquid mixture in the reaction tank is stirred by the air. The activated sludge is agitated by this aeration and becomes suspended. As shown in FIG. 2 and FIG. 3, the diffuser tubes 4 are arranged only on the other side (the side far from the inlet 3) of the reaction tank 2, and generate a swirling flow in the reaction tank 2 by aeration. .

  The reaction tank 2 is provided with a plurality of filter modules 7 for filtering the liquid mixture in the tank to obtain a filtrate. In the example shown in FIG. 2, the waste water treatment apparatus 1 has, for example, nine filter modules 7. The number of filter modules 7 is not particularly limited. The number of filter modules 7 may be N (N is an integer of 2 or more). The plurality of filter modules 7 are connected in parallel by an outflow pipe 8 and an outflow path 11 described later.

  The reaction tank 2 is provided with an outflow path 11 that is connected to the filter module 7 and discharges outflow water (filtrate) from the filter module 7 to the outside of the tank. An outlet pipe 8 is connected to each filter module 7. The outflow pipe 8 is disposed between the filter module 7 and the outflow path 11 and connects the filter module 7 to the outflow path 11. The shape of the outflow pipe 8 may be any shape as long as the filtrate 20 can be introduced into the outflow path 11. The outflow path 11 is a pipe that extends in the reaction tank 2 in the horizontal direction. The base end portion of the outflow passage 11 is closed in the reaction tank 2, and the connection portion 11 a that is the front end portion of the outflow passage 11 passes through the side wall 2 a of the reaction tank 2 and protrudes out of the tank.

  The connection part 11 a of the outflow channel 11 is connected to the upper part of the post-treatment tank 15. The post-treatment tank 15 is a bowl-shaped water tank whose upper surface is opened, for example. The post-treatment tank 15 is filled with a large number of plastic fillers such as sponge cubes 17 in a swingable state. The post-treatment tank 15 contains the filtrate 20 and the sponge cube 17. A small air diffuser 16 is provided at the bottom of the post-treatment tank 15, and aeration is performed from the small air diffuser 16. As described above, the post-treatment tank 15 is filled with a plastic filler such as the sponge cube 17 in a flowable state. The filtrate 20 is directly guided to the outside of the reaction tank 2 and discharged to the upper portion of the post-treatment tank 15 that is aerated by the small diffuser 16.

  A treated water outflow pipe 18 is connected to the lower portion of the post-treatment tank 15. The treated water outflow pipe 18 extends in the vertical direction and has an opening that overflows at the position of the water level in the post-treatment tank 15. In this manner, a pipe that is connected to the bottom of the post-treatment tank 15 and is started up and that overflows at the water level of the post-treatment tank 15 is provided. In this post-treatment tank 15, the small activated sludge floc that has passed through the filter 6 is captured by the sponge cube 17 (filler) layer. The space of the post-treatment tank 15 is smaller than the conventional sedimentation basin. By installing the post-treatment tank 15, the sedimentation basin can be omitted.

  In the wastewater treatment apparatus 1, the mixed liquid in the tank is filtered by the filter 6 of the filter module 7 provided in the reaction tank 2, and the filtrate is discharged from the filter module 7. The waste water treatment apparatus 1 has a structure in which all of the raw water that has flowed into the reaction tank 2 passes through the filter 6 and exits from the outflow path 11 to the outside of the reaction tank 2. That is, the filter 6 of the filter module 7 passes the entire amount of the mixed solution. Here, the “total amount” is meant to include all and almost all of the waste water flowing into the waste water treatment apparatus 1 as a reference. For example, assuming that the amount of wastewater flowing into the wastewater treatment apparatus 1 is 100%, the amount of wastewater (or mixed solution) of 99% is within a range that can be referred to as “total amount”.

  The plurality of filter modules 7 are arranged at a predetermined interval so that their wide surfaces (side surfaces 31 of a frame 30 described later) face each other. Below the filter modules 7, the above-described air diffuser 4 is installed. Due to the swirling flow generated by the aerated air, an upward flow flowing between the filter modules 7 and 7 is generated. Thereby, the functions of stirring in the reaction tank 2, supplying oxygen to the activated sludge, and washing the filter 6 by swinging are exhibited.

  Then, the filtration part in the reaction tank 2 is demonstrated with reference to FIGS.

  As shown in FIG. 3, the filter module 7 includes a frame portion 30 made of, for example, rigid plastic, a support member 40 joined or fitted to the frame portion 30, and a frame portion so as to cover the support member 40. 30 and a filter 6 joined to 30.

  The frame portion 30 is, for example, a thin box-shaped mold frame, and includes two opposing side surfaces 31, a bottom surface 34 that connects the lower side portions of the side surface 31, and an end surface 32 that connects the side side portions of the side surface 31. The side surface 31 is the widest surface and is arranged vertically. The end surface 32 is a surface narrower than the side surface 31. The upper surface 33 of the frame 30 is at a position higher than the water surface of the reaction tank 2 and is opened upward. That is, the upper surface 33 of the frame portion 30 includes an open portion 33a that allows the outside of the filter module 7 to communicate with the internal space. The bottom surface 34 of the frame part 30 is closed. The frame portion 30 may be made of metal, but is preferably made of plastic from the viewpoint of adhesiveness of the filter 6.

  A rectangular opening 31a for allowing the mixed liquid to pass therethrough is formed on the side surface 31 of the frame portion 30, respectively. For example, a rectangular support member 40 is joined or fitted into the opening 31a. These support members 40 are, for example, resin net members. The support member 40 has, for example, a lattice shape and has an opening larger than the opening of the filter 6 described later. Since the opening of the support member 40 is sufficiently large with respect to the opening of the filter 6, the support member 40 is configured not to prevent the mixture liquid from passing through the filter 6. The support member 40 has, for example, a formability. The support member 40 may be made of a hard material that does not deform at all, or may be made of a flexible material. The support member 40 is attached to the filter 6 and is in contact with the filter 6 over the entire surface thereof. The support member 40 supports the filter 6 from the back side of the filter 6.

  The filter 6 is attached to the side surface 31. The filter 6 is attached via the support member 40 so as to cover the opening 31 a of the side surface 31. The filter 6 is bonded to the peripheral edge 31b of the side surface 31, for example. The back surface 6b of the filter 6 is in contact with the support member 40 described above. The surface 6 a of the filter 6 constitutes a filtration surface of the filter module 7.

  The filter 6 is, for example, a woven cloth (filter cloth). The opening of the filter 6 is, for example, in the range of 10 μm to 200 μm. More preferably, the opening of the filter 6 may be within a range of 20 μm to 50 μm, for example. The thickness of the filter 6 can be set arbitrarily. The filter 6 may be made of resin. More specifically, the filter 6 may be made of, for example, polyester, polyethylene, or nylon. The opening of the filter 6 is larger than the pore size of the microfiltration membrane. The opening of the filter 6 is substantially constant regardless of the part. That is, the filter 6 has a uniform opening. The fiber of the filter 6 is a single layer, and there is no complicated gap like a nonwoven fabric.

  In the wastewater treatment apparatus 1, a filter 6 having a larger opening (pore diameter) than a membrane used in a so-called membrane separation activated sludge method (MBR) is used. Therefore, the cleaning effect of the filter 6 by the above-described aerated air (by the upward flow and the accompanying oscillation) is obtained, and the filter 6 is not easily clogged.

  In the filter module 7, a connection pipe 36 is provided at one position on one lower side of the pair of end faces 32. The end of the outflow pipe 8 is connected to the connection pipe 36. The connection port 36a of the connection pipe 36 communicates with the internal space of the filter 6, and the filtrate flows out of the filter 6 through the connection port 36a. Under the liquid surface of the mixed liquid, it is not opened except for the connection port 36a connected to the outflow pipe 8 and the opening 31a covered with the support member 40 and the filter 6, and is closed. The connection pipe 36 or the outflow pipe 8 of the filter module 7 may be provided with a valve 9 (see FIG. 4) capable of allowing and blocking the flow of the filtrate in the inside.

  A method for treating wastewater by the wastewater treatment apparatus 1 will be described. In the wastewater treatment apparatus 1, when wastewater (raw water) containing a substance to be treated such as an organic substance flows into the reaction tank 2, it is mixed with the activated sludge in the reaction tank 2, and the substance to be treated by microorganisms in the activated sludge in the mixed solution. The mixed liquid of raw water and activated sludge in which the material to be treated is decomposed enters the filter module 7. Accordingly, activated sludge particles larger than the opening of the filter 6 are captured by the filter 6, and the subsequent liquid (filtrate) flows into the post-treatment tank 15 through the outflow pipe 8 and then the outflow path 11. In the reaction tank 2, the filter 6 is swung by aeration from below the filter module 7, and filtration is performed while separating the filtered activated sludge particles. On the other hand, in the post-treatment tank 15, fine activated sludge particles that have passed through the filter module 7 come into contact with the sponge cube 17 by aeration and are trapped in the pores and gaps of the sponge cube 17, and become purified treatment water. It flows out from the treated water outflow pipe 18. Thus, according to the waste water treatment apparatus 1, the mixed solution 10 is filtered by the filter module 7 provided in the reaction tank 2, and the MLSS concentration in the reaction tank 2 is increased.

  Then, with reference to FIG. 4, the washing | cleaning method of the filter 6 in the waste water treatment apparatus 1 is demonstrated. In the wastewater treatment apparatus 1, clogging of the filter 6 is difficult to occur during normal operation, but clogging may occur. When clogging occurs, for example, the water level in the reaction tank 2 rises. In such a case, forced cleaning of the filter 6 is required. In the method for cleaning the filter 6 in the waste water treatment apparatus 1, ultrasonic cleaning is used. Therefore, an ultrasonic generator 50 (see FIG. 4B) is prepared as an incidental facility of the wastewater treatment apparatus 1.

  More specifically, in a state where the filter 6 is immersed in the liquid, an ultrasonic wave is generated by the ultrasonic generator 50, and the filter 6 is cleaned by the ultrasonic wave transmitted through the liquid. The filter 6 may be washed in a state where the filter module 7 is immersed in the mixed solution. In that case, the filter 6 may be cleaned during the operation of the waste water treatment apparatus 1 (during the water flow treatment), or the filter 6 may be cleaned while the operation of the waste water treatment apparatus 1 is stopped. The filter 6 may be washed in a state where the filter module 7 is detached from the waste water treatment apparatus 1 and the filter module 7 is immersed in a liquid (such as clean water W) in another washing tank. Alternatively, the filter 6 may be removed from the filter module 7 and the filter 6 may be subjected to ultrasonic cleaning.

  Any known device can be used as the ultrasonic generator 50. For example, as shown in FIG. 4B, an apparatus having a cleaning tank that stores clean water W and the like, and an ultrasonic generator 51 attached to the wall surface of the cleaning tank may be used. A handy type (portable type) device may be used in which an ultrasonic wave generator is provided at the tip of a rod-shaped body. The ultrasonic generator is an oscillator that generates ultrasonic waves.

  For example, in the waste water treatment apparatus 1 shown in FIG. 2, when cleaning the filter 6, the ultrasonic wave generator of the ultrasonic wave generator is positioned in the frame part 30 through the open part 33 a of the upper surface 33 to transmit the mixed liquid 10. You may wash | clean the filter 6 from the back surface 6b side with an ultrasonic wave. As the ultrasonic generator, the above-described handy type (portable type) apparatus may be used. At this time, the support member 40 is vibrated by the ultrasonic wave transmitted through the mixed liquid 10, and the peeling effect of sludge and biofilm is enhanced.

  The filter 6 may be cleaned by stopping the operation of the waste water treatment apparatus 1, but the filter 6 can also be cleaned without stopping the operation of the waste water treatment apparatus 1. For example, as shown in FIG. 4 (a), only one of the nine filter modules 7 (M = 1, the second one from the left) is cleaned, and the remaining eight ( Filtration by the (NM) filter modules 7 may be continued. At this time, the filtration by the filter module 7 can be stopped by closing the valve 9 of the pipe connected to the filter module 7 to be cleaned. The number (M) of filter modules 7 to be cleaned may be an integer of 1 or more and 8 or less (less than N). The filter module 7 may be washed in the mixed solution 10, or the filter module 7 may be removed and washed outside the reaction tank 2.

  When removing the filter module 7 and washing the filter 6, for example, as shown in FIG. 4B, the filter module 7 is immersed in a washing tank storing the water W and directed from the ultrasonic generator 51 to the water W. To oscillate ultrasonic waves. Also in this case, a direct cleaning effect on the filter 6 and an indirect cleaning effect via the support member 40 are obtained.

  According to this cleaning method for the filter 6, the ultrasonic waves generated by the ultrasonic generator 50 are transmitted through the liquid and transmitted to the filter 6. The ultrasonic waves act on the filter 6, and sludge and biofilm attached to the filter 6 are peeled off from the filter 6. Sludge and biofilm attached to the inside of the filter 6 and the back surface 6b side (filtrate 20 side) that cannot be washed with aerated air can also be peeled off. Therefore, the filter 6 can be efficiently washed in the wastewater treatment apparatus 1 to which the filter concentrated activated sludge method is applied.

  Ultrasonic waves are transmitted to the support member 40 and vibrate the support member 40. For example, there is an effect that the support member 40 serves as a vibration medium to vibrate the filter 6. Therefore, peeling of sludge and biofilm is promoted, and the filter 6 can be cleaned more efficiently.

  When cleaning the filter module 7, ultrasonic cleaning can be performed through the open portion 33 a of the upper surface 33 of the frame portion 30. For example, ultrasonic cleaning can be performed with the filter module 7 installed. Since it is not necessary to remove the filter module 7 from the waste water treatment apparatus 1, the filter 6 can be easily and easily washed.

  In the wastewater treatment apparatus 1, the filters 6 of the M filter modules 7 can be washed while filtering with the (N−M) filter modules 7. Therefore, the ultrasonic cleaning of the filter 6 can be performed without stopping the operation of the waste water treatment apparatus 1. In this case, although the treatment capacity of the waste water treatment apparatus 1 temporarily decreases, the waste water treatment does not stop, which is advantageous compared to the case where the waste water treatment is completely stopped. Further, the exfoliated sludge and biofilm may be introduced into the post-treatment tank 15 and further processed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the configuration of the wastewater treatment apparatus 1 can be changed as appropriate. Nitrogen removal may be possible by providing the reaction tank 2 with a fixed or floating type microorganism adhesion carrier. As the structure of the filter module 7, a known filter structure other than the above-described embodiment (structure shown in FIG. 3) may be adopted.

  Only one filter module 7 may be provided for one wastewater treatment apparatus 1. The filter module 7 may be a module of a type in which the upper surface 33 is not opened and is completely immersed. In that case, ultrasonic cleaning may be performed from the surface 6a side of the filter 6 by a portable ultrasonic generator, or the filter 6 may be ultrasonic cleaned after the filter module 7 is removed. .

  In the filter module 7, the shape and material of the support member 40 can be changed as appropriate. The support member 40 is not limited to a lattice shape, and may be a cross-shaped member attached to the filter 6 (a member in which a longitudinal member and a transverse member intersect). The support member 40 may be omitted.

(Filter cleaning test)
A simulated drainage test was conducted and a filter cleaning test was conducted. A simulated drainage test was conducted for about 4 months using a 60 L lab scale reactor. Four box filter modules made of PVC with filters attached to both sides were installed at the outlet of the reaction part of a 60 L capacity square reactor (reaction part 60L, sedimentation part 1.98L) (only three of them) Used for water flow test). As simulated drainage, artificial sewage adjusted with soluble starch or the like was used. Simulated waste water was passed at 250 L / day. The test results are shown in FIG.

The following were used as a filter and a support member.
Filter: T420-27 (wire diameter 27 μm, mesh opening 33 μm) (manufactured by Teijin Limited)
Support member: Tricarnet N-34 (mesh size 34 mm × 34 mm, thickness 4 mm) (Dainippon Plastics)

The filter was appropriately replaced until the 58th day after the start of water flow, but the water was passed without replacing the filter after the 58th day. On day 104, an increase in the water level of the reactor was confirmed, and it was determined that clogging occurred. Therefore, the filter was removed and ultrasonic cleaning (38 kHz, 15 min) was performed. After ultrasonic cleaning, the filter was installed again and water flow was resumed, and it was confirmed that the permeation flux before clogging could flow for 2 weeks. The following was used as an ultrasonic cleaner. Shown with cleaning conditions.
Ultrasonic cleaner: US-75KS (manufactured by SND Co., Ltd.), (AC100V, 1200W, 38kHz, (strong) 960W, washed for 15 minutes)

Table 1 shows the amount of sludge adhering to the filter surface before and after ultrasonic cleaning. This is a measurement of the amount of sludge adhering to the surface by scraping 2 cm ² of the surface of the filter surface at an arbitrary place with cardboard. Before ultrasonic cleaning, sludge adherence was confirmed inside the filter (on the back side), but after ultrasonic cleaning, no sludge adhered to the investigated part.

DESCRIPTION OF SYMBOLS 1 Waste water treatment apparatus 2 Reaction tank 3 Inlet 6 Filter 7 Filter module 8 Outflow pipe 9 Valve 10 Mixture 11 Outflow path 15 Post-treatment tank 20 Filtrate 30 Frame part 31 Side surface 33 Upper surface 33a Opening part 40 Support member 50 Ultrasonic wave generation Device 51 Ultrasonic generator

Claims (4)

In the wastewater treatment apparatus in which at least one filter module provided with a filter having an opening of 10 μm or more is provided in a reaction tank that contains a mixed liquid containing activated sludge in a suspended state and a wastewater agitated by aeration, A filter cleaning method,
A method for cleaning a filter, wherein the filter is cleaned by the ultrasonic wave that is transmitted through the liquid by generating an ultrasonic wave with an ultrasonic generator while the filter is immersed in the liquid. The filter module includes a support member that has an opening larger than the opening of the filter and is attached to the filter to support the filter,
The method for cleaning a filter according to claim 1, wherein, when cleaning the filter, the support member is vibrated by the ultrasonic wave transmitted through the liquid. The filter module includes a frame portion including a side surface to which the filter is attached and an upper surface that is higher than the water surface of the reaction tank and is open upward.
When cleaning the filter, the ultrasonic generator of the ultrasonic generator is positioned in the frame through the opening on the upper surface, and the filter is moved from the back side by the ultrasonic wave transmitted through the liquid mixture as the liquid. The filter cleaning method according to claim 1, wherein the filter is cleaned. The at least one filter module has N (N is an integer of 2 or more) filter modules;
While filtering the M filter modules among the N filter modules (M is an integer greater than or equal to 1 and less than N) while the filtration of the M filter modules is being cleaned by the ultrasonic wave, ( The filter washing | cleaning method as described in any one of Claims 1-3 which performs filtration by a NM) filter module.

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